A four-stage construction is presented for illustrating the characteristic clinical pattern and profile over the years in the average, 'classical' rett syndrome (RS) patient. The staging system was applied and evaluated in the 29 Swedish RS cases who now have passed age 13 (median 18). We also discuss the diagnostic pitfalls we have met and the conditions that need to be considered in the differential diagnosis.

Incidence of sudden death in Rett syndrome is greater than that of the general population and cardiac electrical instability is a prime suspect cause. Our study shows that girls with Rett syndrome had significantly lower heart rate variability (marker of autonomic disarray) and longer corrected QT intervals compared with an age-matched group of healthy girls. These abnormalities increased with advancing stages of the syndrome. These findings suggest a possible role of cardiac dysfunction in the sudden death associated with Rett syndrome.

The clinical variability of Rett syndrome, associated with mutations in the MECP2 gene, varies from classically symptomatic female patients to asymptomatic female patients, and male patients who have none of the diagnostic features considered pathognomonic of this disease. Multiple factors contribute to this variability. In our studies, mutations closer to the amino-terminus, prior to amino acid 255, led to severe clinical manifestations, such as inability to walk, severe dysphagia, and urinary organic acid abnormalities, compared with mutations toward the carboxyl-terminus. However, we found no correlation between severity and mutation type (missense versus nonsense). Despite the importance of mutation location to clinical severity, the widely varying severity within the same mutation suggests that in females, X-chromosome inactivation or other epigenetic phenomena also have roles in determining severity. We propose that stages 1 and 2 of the disease are a consequence of failed, time-linked, postnatal expression of MeCP2 in cerebellar neurons. This, in association with glutamate N-methyl-D-aspartate receptor-mediated neuroexcitotoxic injury to the differentiating neurons, results in the transient age-specific autistic-like behavior, motor, and cognitive dysfunction associated with these stages.

Rett syndrome is a neurological disorder almost exclusively affecting females. Information on its genetic basis has recently become available. However there is little information on the burden and impact of this disorder on the family despite the apparent variability in phenotype. The purpose of this study was to obtain information on the burden and impact of Rett syndrome by examining the functional abilities, medical needs and use of medical, therapy and accommodation services in the sample.

Rett syndrome is a severe neurodevelopmental disorder of unknown aetiology. A prolonged QT interval has been described previously in patients with Rett syndrome. To investigate QT prolongation and the presence of cardiac tachyarrhythmias in Rett syndrome electrocardiography and 24 hour Holter monitoring were performed prospectively in a cohort of 34 girls with Rett syndrome. The corrected QT value was prolonged in nine patients. Compared with a group of healthy controls of a similar age range, the patients with Rett syndrome had significantly longer corrected QT values. Clinical severity was not a predictor for prolonged QT intervals in the Rett syndrome cohort. The prolonged QT syndrome is a serious and potentially lethal cardiac disorder and should be considered in all girls with Rett syndrome.